Ultrasonic sensors has been widely used in industry, national defense, fire protection, electronics and other different fields the like. A typical kind of ultrasonic sensors are ultrasonic fingerprint sensors used in electronic devices such as smart phones or tablet computers. Ultrasonic sensors are also known as transceivers or transducers which work on a principle similar to radar or sonar, which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. The ultrasonic sensors can generate high frequency sound waves and evaluate the echo which is received back by the sensor. For example, the sensors can measure the time interval between sending the signal and receiving the echo to determine the distance to an object.